Heavy Metal Deposition Research Articles

Electrochemical Column Cell for Continuous Oxidative Inactivation of Pathogens and Reductive Removal of Toxic Heavy Metals

A solar-driven electrochemical column (EC) was developed for cathodic sequestration remediation of heavy metals (HMs) and anodic electroporative inactivation of pathogenic bacteria (PB) with continuous flow capacity for sustainable production of drinking water from wastewater. The method produces "revitalized drinking water" by keeping its natural mineral nutrients boosted with dissolved oxygen. The EC was constructed with graphene oxide (GO) synthesized via photoassisted electrochemical oxidation of CF (PEGO-CF) as the cathode and phytoreduced GO (RPEGO-CF) as the anode. In the EC, effluent is passed upward through the microchannel of CF electrodes to obtain a higher contact time with water molecules, enabling deposition of HMs and oxidative inactivation of PB, collectively termed electroadsorptive dialysis (EAD). PEGO-CF and RPEGO-CF stacked inside the EC resulted in the increased surface area and thereby the removal efficiency. Reactive oxygen species (ROS) produced at the anode damaged the bacterial cell sheath, while the oxygen functional group and the cathodic negative potential had a concurrent effect in "sequestration" of HMs. Density functional calculations showed that PEGO might transfer an electron from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) under applied negative potential leading to internal system crossing to the vacant d-orbitals of HMs, allowing for simultaneous coordination and deposition. The EC produced 313 L of revitalized water from wastewater augmented with 500 μg L-1 HMs and 107 CFU mL-1 pathogenic bacteria (Escherichia coli and Staphylococcus aureus). Only a 3.6 J energy investment produced 1 L of revitalized water, which is ∼2000 times less than the usual energy consumption by electroporation and the lowest value obtained to date for bacterial inactivation with heavy metal removal. Laboratory-to-industrial scale-up calculations were performed for this water-purifying technology involving a water-energy nexus, promising high-efficiency bacterial inactivation, and HM remediation to obtain energy-efficient clean and revitalized water.

Burdur ilinde Karayollarının Yakınından Toplanan Bazı Karayosunu Örneklerinde Ağır Metal Seviyelerinin Belirlenmesi

The main sources of atmospheric heavy metals deposition are agricultural activities, fossil fuels, central heating stations and the exhaust gases of motor vehicles. In this study, the total of 29 mosses samples were collected from contaminated points near the Isparta-Antalya, Burdur-Denizli, Burdur-Afyonkarahisar, Burdur-Fethiye (Muğla) and Burdur-Antalya highways (2-20m) and uncontaminated areas in 2012. Samples were analyzed by flame and graphite furnace atomic absorption spectrometry (AAS) later microwave digestion methods. The highest accumulation levels detected as µg.g−1 Fe (1419.02)>Zn (158.44)>Mn (362.77)>Ni (109.53)>Cr (60.51)>Pb (30.38)>Cd (35.866)>Cu (25.17) for mosses. Element levels are differ depending on moss species and the location of collecting localities.

Trends of nutrients and metals in precipitation in northern Germany: the role of emissions and meteorology

We analyzed the precipitation chemistry for a maritime region in northern Germany (Schleswig–Holstein) from 1997 to 2017 in order to reveal temporal and spatial patterns and to evaluate the role of meteorological factors relative to emission reductions in Germany and Europe. Therefore, we applied several statistical methods such as time series decomposition, principal component, and redundancy analysis. We extracted two main groups: (i) a marine group (Cl, Na, Mg) that was related to natural processes like sea spray input and (ii) an anthropogenic group (Pb, Cd, As, Zn, and nitrogen species) with a terrestrial subgroup (Fe, Al, Mn), which were both related to emissions. These groups were valid for the spatial, seasonal, and annual trend data. Other elements, like Ca, K, total P, and sulfate, were influenced by natural and anthropogenic processes. The seasonal variation of ammonium deposition was caused primarily by ammonia emissions and ancillary by precipitation. Most heavy metals as well as sulfate, nitrate, and ammonium showed decreasing trends in concentrations and deposition fluxes. Only Hg did not show any trend. The decreasing depositions of sulfate and total nitrogen were correlated to emission reductions in Germany. The deposition of most heavy metals was influenced by emission reductions on European scale and meteorological factors such as wind speed and humidity. Hg did not show any correlation with the emission time series in Europe. Instead, it was correlated to the NAO index and wind, implying that global emissions and transport pathways determine the temporal development of Hg depositions. Overall, the study reveals that emission reductions positively influence regional depositions for most investigated substances. The regional spatial patterns of depositions were also influenced by local meteorological factors.

Extended divergence estimates and species descriptions of new craspedid choanoflagellates from the Atacama Desert, Northern Chile

In contrast to previous perspectives, hypersaline environments have been proven to harbour a variety of potentially highly adapted microorganisms, in particular unicellular eukaryotes. The isolated, hypersaline waterbodies in the Atacama Desert, Northern Chile are exposed to high UV radiation and deposition of toxic heavy metals, making them of great interest regarding studies on speciation and evolutionary processes. In the past two years, among a variety of other protist species, five new species of heterotrophic choanoflagellates were described and analysed from this area, showing an adaptation to a broad range of salinities. Morphological data alone does not allow for species delineation within craspedid species, additional molecular data is essential for modern taxonomy. In addition, molecular clock analyses pointed towards a strong selection force of the extreme environmental conditions. Within this study, we describe three additional craspedid choanoflagellate species, isolated from different aquatic environments. Phylogenetic analyses show two distinct clades of choanoflagellates from the Atacama, suggesting two independent invasions of at least two ancestral marine species, and, as indicated by our new data, a possible dispersal by Andean aquifers. The extended molecular clock analysis based on transcriptomic data of choanoflagellate strains from the Salar de Llamará, a hypersaline basin within the Central Depression of the Atacama Desert, reflects colonisation and divergence events which correspond to geological data of the paleohydrology.

Heavy metal accumulation and potential ecological risk assessment in sediments from the southwestern Konya district (Turkey)

It is aimed to determine the heavy metal concentrations and sources accumulated in the sediments of the creeks in the region as a result of geological factors and to be a reference study before the mining exploration and operation activities to be carried out in and around the study area located in the southwestern Konya district of Turkey. Chemical analyses were carried out on 24 rock samples representing the geological characteristics of the region and 8 stream sediment samples taken from important creeks. Chemical analysis results were evaluated using basic statistical methods and pollution indices. As, Pb, Zn, and Mn concentrations were determined as “unpolluted to moderately polluted” according to the geoaccumulation index. According to the contamination factor, the accumulations for As, Pb, Zn, Mn, Fe, and Al concentrations were determined as a “moderate factor.” It is determined as “low risk” according to the potential ecological risk index. Heavy metals in the region were ranked from the lowest risk to the highest as Ni <Cr <Zn <Mn <Hg <Cu <Pb <Cd <As. The accumulation of heavy metal around the creek deposits is related to the geological processes and climatic events. It is understood that heavy metal deposits in the region are formed due to geological factors, and geological factors have an important role in heavy metal accumulation in the sediments of the creeks.

Does combined heavy metal stress enhance iron plaque formation and heavy metal bioaccumulation in Kandelia obovata?

Iron plaque (IP) has significant impact on rhizosphere environment, and affects the uptake and translocation of heavy metals in plants. However, information on IP formation and heavy metal bioaccumulation for mangrove plants under combined heavy metal stress is currently limited. Based on a 120-day pot experiment, this study explored the temporal changes of IP formation on root surface of Kandelia obovata, and heavy metal bioaccumulations under combined heavy metal stress of Cu, Pb and Zn. The results showed that IP formations on root tip, middle and basal roots were improved with combined heavy metal stress and treatment time (root tip: 0.49−0.61 mg g−1 to 2.55–4.77 mg g−1; middle root: 0.27−0.31 mg g−1 to 3.01–4.22 mg g−1; basal root: 0.16−0.23 mg g−1 to 2.24–4.10 mg g−1). IP formation was accompanied with improved depositions of Cu and Pb on root surface, regardless of root tip, middle and basal roots. IP and roots deposited large amounts of Cu (24.97–69.52 μg g-1, 9.39–154.75 μg g−1), Pb (8.35–84.53 μg g-1, 12.29–191.49 μg g-1) and Zn (85.71–139.19 μg g-1, 51.07–195.65 μg g−1), inhibiting their translocations to aboveground leaves. Based on subcellular distribution and chemical forms of heavy metals in roots, the improved depositions of phosphate-integrated Cu (6.77 %–25.13 %), oxalate-integrated Pb (34.89 %–57.88 %), as well as pectate- and protein-integrated Zn (14.22 %–35.41 %) were detected in root cell vacuoles. In conclusion, the combined heavy metal stress enhanced IP formation and heavy metals deposition (especially for Cu and Pb) on root surface, and improved their vacuolar sequestration and chelation in roots of K. obovata.

The effect of heavy metal pollution on urban ecosystem and the evaluation of different land classifications; in Bingöl city/Turkey

PurposeOne of the problems that urbanization creates on the ecosystem is the increase of heavy metal accumulation of the urban lands. Due to constant urbanization and industrialization in many parts of the world, metals are constantly spreading to the environment and pose a great threat to human health. The purpose of the study is to determine the effect of heavy metal accumulation values of the lands located in Bingöl city center on the urban ecosystem by examining them in terms of zonal and land-use classification.Design/methodology/approachThe research was conducted on 30 samples taken from five zones and six land-use classes (traffic area-TA, school area-SA, commercial-industry area-CA, green space-GS, residential area-RA and open space-OS). Heavy metal deposits of soil samples were determined in accredited laboratories using the Inductively Coupled Plasma – Mass Spectrometer (ICP-MS) and Atomic Absorption Spectrometer (AAS) device. The study employed the SPSS program for statistical analysis of laboratory results, and ArcGIS Pro programs were used to determine spatial pollution distribution.FindingsAlthough the heavy metal contents of soil samples pose no problems in terms of national and international standards, a number of zones carry risks for the future. In the analyzes, traffic and settlement area soils in terms of land-use classifications and Zone 5 soils in terms of zonal distribution were determined as ecologically risky areas.Originality/valueThe study provided suggestions on what should be done to use the results of the research in planning the physical development of the city.

Bulk Deposition and Source Apportionment of Atmospheric Heavy Metals and Metalloids in Agricultural Areas of Rural Beijing during 2016–2020

While atmospheric deposition plays a vital role in cleaning air pollutants, it also supplies toxic heavy metals and metalloids (MMs) to the receiving terrestrial and aquatic ecosystems and threatens human health through food chains. To characterize the input of atmospheric deposition to agricultural soils, bulk rain samples were collected on an event basis at a rural site in the North China Plain during 2016–2020. The results show that higher concentrations of MMs in bulk rain samples were associated with western and southern air masses passing polluted areas. In addition, the annual deposition flux of MMs tends to decline during the study period, coinciding with the inter-annual variations of particulate matter rather than the precipitation amounts. Of note, the deposition flux of MMs that exist entirely in fine particles declined significantly compared to those that exist in coarse particulate form, indicating that the clean air actions implemented in recent years were highly effective in reducing ambient MMs from anthropogenic emissions. The positive matrix factorization receptor model was also applied to the whole data set for bulk depositions and five sources were identified as agricultural (biomass burning and soil), dust, coal combustion, industrial and traffic emissions. These factors contributed 41%, 24%, 21%, 9% and 5% of the chemical components in bulk depositions, respectively. Future control strategies should tighten the emissions from combustion and soil/dust in the North China Plain to protect agriculture from atmospheric MMs depositions.

Source and spatial distribution of airborne heavy metal deposition studied using mosses as biomonitors in Yancheng, China.

Naturally growing mosses have been successfully used as biomonitors of atmospheric heavy metal (HM) deposition. In recent years, with rapid economic development, environmental pollution in Yancheng, a coastal city in central Jiangsu Province, China, has become increasingly serious. However, to date, there have been no reports on atmospheric HM deposition in Yancheng. In this study, we investigated the HM concentrations and Pb isotopes in the moss Haplocladium microphyllum (Hedw.) Broth. from Yancheng and analyzed their main sources. The concentrations of HM in mosses from Yancheng were higher than those recorded in other studies of mosses from HM smelting regions and pollution-free areas of Eurasia and Alaska. The contamination factor value suggested that the pollution level of Cd was the highest. The pollution load index indicated that the studied area was severely contaminated with Cd, Cr, Pb, Zn, V, Ni, and Cu. Positive matrix factorization was employed to identify the contamination sources of HM and apportion their source contributions in mosses. The contributions of the natural source, together with manufacturing and construction, metal processing and chemical industries, traffic emissions and fuel burning in industrial activities, and agricultural activities, accounted for 53%, 33%, 12%, and 2%, respectively. The Pb isotopic ratios in the mosses (1.125-1.164 for 206Pb/207Pb, 2.059-2.148 for 208Pb/206Pb) further proved that metal processing and traffic emissions were the main sources of Pb contamination. These results are useful for developing various effective measures to prevent and reduce atmospheric HM deposition in Yancheng.

Variations in local heavy metal concentrations over the last 16,000 years in the central Atacama Desert (22°S) measured in rodent middens

Mining is a major industry in the Atacama Desert, one of the world's leading regions for copper and other minerals. Intense industrialization of copper mining in the mid-twentieth century has likely led to significant environmental pollution through the deposition of heavy metals in the hyperarid Atacama, but how heavy metal pollution has changed over time in arid regions have rarely been assessed. Here, we analyzed both modern and ancient fecal pellets from paleomiddens collected in the central Atacama for heavy metals and by comparing current heavy metal concentrations with pre-industrial ones, we establish ecological baselines for such pollution. Sixteen paleomiddens spanning the last 1000 years from multiple localities in the eastern Calama Basin (22°S) show elevated concentrations of Cu and As in modern compared to older middens, and that heavy metal, alkali metals and alkaline earth metals show positive correlations with each other. Heavy metals also tend to be higher in paleomiddens collected along perennial rivers in comparison to those collected from surrounding ranges, irrespective of sample age. Twenty paleomiddens spanning the last c. 16,000 years from a single locality (El Hotel) between the Calama and San Pedro de Atacama basins were used to establish long term variations in plant communities and associated heavy metals since the last glacial termination. Results show that heavy metal concentrations including Cr, Mo and B vary over time and tend to be higher in paleomiddens for which Cactaceae are more abundant whereas those dominated by annuals show less of an effect from trace metals. Our results imply that climate change-driven plant community composition plays a key role in explaining how contamination varies in these desert ecosystems and show that paleomiddens are a unique and unexplored source for understanding how heavy metals vary over time. Given their ubiquity in many of the world's arid regions, they can be used to establish long-term ecological baselines to compare against human alterations.

Different cadmium levels alter growth and antioxidant defense response in Cedrela fissilis and Colubrina glandulosa

The Seasonal Semideciduous Forest (SSF) of SE Brazil is an extensively fragmented biome and continuously receives the deposition of heavy metals, such as cadmium (Cd). This metal, depending on its concentration, may cause oxidative stress in different plant species. In this study, we analyzed the effects of different Cd concentrations on the antioxidant activity and initial development of two SSF native species. Cedrela fissilis and Colubrina glandulosa seedlings were grown in different concentrations of Cd: 0 (control), 300, 700, and 1000 mg L−1. After 10 days, the concentrations of Cd significantly reduced the length of both species and the dry mass in C. fissilis. The superoxide dismutase (SOD) and peroxidase (POD) activities of C. fissilis were reduced by Cd doses, while catalase (CAT) activity and proline concentration were increased. In C. glandulosa, the SOD activity showed a hormesis response and POD increase in 1000 mg L−1 of Cd. The results showed that C. glandulosa had greater developmental plasticity and maintenance of biomass than C. fissilis, even when MDA values were high, suggesting that they were balanced by the higher efficiency of the enzymatic antioxidant system. In C. fissilis the mechanism of action against oxidative stress was partially enzymatic (CAT activity) and partially non-enzymatic (proline). These results showed that both species were sensitive to Cd exposure; however, they present different responses and tolerance levels under different concentrations of the metal. The parameters analyzed in these species can be used as suitable biomarkers for monitoring the toxicity of Cd in the SSF.

Assessing the relevance of atmospheric heavy metal deposition with regard to ecosystem integrity and human health in Germany

BackgroundThe critical values for heavy metal fluxes for protecting the human health and ecosystem’s integrity in Germany, especially the Federal Immission Control Act (BImSchG in Gesetz zum Schutz vor schädlichen Umwelteinwirkungen durch Luftverunreinigungen, Geräusche, Erschütterungen und ähnliche Vorgänge (Bundes-Immissionsschutzgesetz-BImSchG), 1974/2020) with its implementing ordinances (especially the 39th BImSchV in Neununddreißigste Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes Verordnung über Luftqualitätsstandards und Emissionshöchstmengen vom 2. August 2010, zuletzt geändert durch Art. 2 V v. 18.7.2018 I 1222, 2010, 2018), the Federal Soil Protection Ordinance (BBodSchV in Bundes-Bodenschutz- und Altlastenverordnung (BBodSchV) (GBBl. I S. 1554 vom 12. Juli 1999, zuletzt durch Artikel 3 Absatz 4 der Verordnung vom 27. September 2017 (BGBl. I S. 3465) ge-ändert, 1999/2015) and the Technical Instructions on Air Quality Control (Luft in Erste Allgemeine Verwaltungsvorschrift zum Bundes–Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft – TA Luft), 2002), were analysed, assessed with regard to the possibilities and applicability of the risk assessment, and were prepared for evaluation in comparison to the respective atmospheric deposition modelled with the chemical transport model LOTOS-EUROS. For a comparison of the critical values, the critical loads for cadmium, lead and mercury inputs were updated for Germany on a scale of 1:1 Mio, and critical loads for additional heavy metals (arsenic, copper, zinc, chromium and nickel) were computed, respectively. Due to the methodological differences of their derivation, the critical values of the individual regulations are only conditionally comparable to one another and to the critical loads. Sometimes major differences exist due to different levels of protection, various protective goods and the effect relationship. Only with the critical load calculations, inputs and outputs can be balanced.ResultsFor two unregulated metals (thallium and vanadium) a preliminary rough estimate of the risk of inputs in the receptors was provided as a calculated balance for in- and acceptable outputs. The uncertainty analysis shows, that the highest deviations occurred in the metal contents in plants used to calculate the output through the harvesting of the biomass. The critical load calculation has the highest sensitivity to changes in the pH value. The critical loads for heavy metal fluxes for protecting the human health (CL(M)drink) and ecosystem’s integrity CL(M)eco) for arsenic, nickel, zinc and chromium were not exceeded in Germany for 2009–2011. CL(M)drink and CL(M)eco are exceeded by Hg and Pb inputs, especially in the low rainfall regions of Germany (Brandenburg, lowlands of Saxony-Anhalt, Leipzig Bay, Ruhr valley) with wood vegetation; in addition CL(Cu)eco is exceeded by copper deposition 2010 in the area surrounding Berlin and in the Ruhr valley. The critical loads for cadmium for the protection of drinking water CL(Cd)drink and for the protection of human food from wheat products CL(Cd)food are not exceeded in the German data set due to atmospheric deposition in 2010, but in the worst-case scenario the maximum atmospheric deposition in 2010 could exceeded the lowest CL(Cd)drink and CL(Cd)food.ConclusionsThat assessment of risks was based on deposition from the atmosphere, which represents only a fraction of the inputs compared to the inputs from the use of fertilisers and other sources. This study suggests the conclusive recommendation to methodically deepen and broaden the assessment and evaluation of atmospheric deposition. This is especially true for the spatial validation and specification of exposure for ecosystem types.

Heavy metal deposition through precipitation in Kazakhstan

The active development of industry, primarily mining and metallurgical, as well as energy, is accompanied by significant emissions of pollutants into the atmosphere. We collected data and analyzed the intake of heavy metals (HM) of lead (Pb), copper (Cu) and arsenic (As), cadmium (Cd) in precipitation (wet deposition) on typical natural Kazakhstan ecosystems. The average Pb, Cu, As and Cd wet deposition was 3.80 ± 1.52, 16.11 ± 1.48, 0.96 ± 0.84 and 0.88 ± 0.44 μg/L, respectively, with a large variation among the different sites of Kazakhstan. In addition, we identified the most significant industrial areas in the republic and determined the concentrations of the listed metals in the precipitation for each of them. The relationship between these concentrations and industrial activity in the regions, and the presence of a mutual correlation between them were also investigated. We obtained that the atmospheric deposition of Pb, Cu and As were higher in the central industrial areas (Dzhezkazgan, Balkhash), as well as in the south (Chimkent) and in the east (Ust-Kamenogorsk), where large mining and metallurgical enterprises are located. In these cities, there are high concentrations of pollutants (PS) in the atmosphere, exceeding the maximum permissible concentrations (MPC) by several times. Significant sedimentation of pollutants, primarily HM, is noted, adversely affecting soils and surface runoff. The total deposition of heavy metals on snow cover was determined. We obtained that the average total deposition for Pb, Cu, As and Cd was 4.4 ± 1.28, 20.6 ± 1.43, 3.23 ± 0.81 and 1.03 ± 0.47 μg/L. Calculations performed for comparable time intervals showed that dry deposition is two to five times greater than wet deposition and the smaller the precipitation in the region, the greater the dry deposition, ceteris paribus. At the level of climate assessments, it is shown that there is a transboundary transfer of heavy metals from both the territory of Kazakhstan from the territory of Russia.

Polluted Landfill adaptation into agricultural soil: heavy metal phytoremediation with Indian Black Mustard (Brassica Nigra) and Dolomitic Lime Fertilizer.

Bio-medical and electronic waste accumulation from industry and anthropogenic sources is deposited at landfill sites over the years, possessing waste degradation into heavy metal deposition in soil such as Cd, Ni, Pb, which is detrimental to the developing embryo development and affects respiratory function. The hyper-accumulator herb, such as Indian mustard ( Brassica Nigra), which was able to absorb heavy metals from the soil and water and wipe out soil after a period of time and disposed of it. Dolomitic Lime Fertilizer is a Inorganic compound derived from mixture of calcium carbonate (caco3) and magnesium carbonate (mgco3) are used for the sustained agriculture. The Extraction of heavy metals along with Dolomitic lime helps to increase the nitrogen fixation rate in soil and reduce the acidity nature of the soil also acts as a soil conditioners. They provide eco-friendly, cheap and renewable resource for the subsequent years. Phytoremediation of contaminated sites is requires low cost and more renewable compared to remediation strategies that involve removing polluted soil constituents.

THE PHYSIOLOGICAL AND CELLULAR STUDY OF TRITICUM TURGIDUM GROWN IN AMENDED SOIL WITH SEWAGE SLUDGE (URBAN AND INDUSTRIAL) IN OPEN FIELDS UNDER SEMI-ARID CLIMATE CONDITIONS

A field experiment was conducted to demonstrate the beneficial and negative aspects of sewage sludge application on wheat and to determine the way of heavy metals in the sludge-soil-plant system. Two types of sewage sludge (urban and industrial) were applied at different rates (5, 25, 50 and 100 t dry matter (DM) per ha). Results showed that growth and yield have been improved by sewage sludge use. However, sewage sludge applications modified the content of heavy metals in plant tissues especially for industrial sewage sludge and high rates where significant accumulations including Co, Cr and Pb, were detected mainly in the roots. This has been coupled by an alteration of the root cellular ultra-structure and the presence of heavy metal deposition as electron-dense granules and crystals.

Nitric Oxide as a Savior Molecule Against Stress Induced by Chromium and Cadmium

Heavy metals (HMs) pollution is one of soil problems imposing great agronomic challenges leading to obstacles in ascertaining food safety. The deposition of HMs beyond permissible limits due to their uses in various agricultural, industrial and household purposes, greatly affect the soil fertility and physio-biochemical activities of plants growing in such soils. Among HMs, cadmium (Cd) and chromium (Cr) are very toxic, non-essential heavy metals whose concentrations have built-up recently in our environment due to several manmade activities. These elements enter into living organisms either by absorption through plants or are directly consumed by animals or microbes. They induce various morphological and physio-biochemical changes in plants ranging from seed germination, growth, nutrient uptake, photosynthesis to hormonal interactions. Excess reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation are two important markers of nitro-oxidative stress during heavy metal stress. Plants counteract by activating defence responses by inducing expression of antioxidant enzymes like (CAT, SOD, APX) and antioxidant compounds like Vitamin C and GSH. Nitric oxide (NO) is one of the active gaseous molecules generated during nitro-oxidative stress induced by HMs like Cd and Cr. NO is generated in the plants by diverse enzymatic and non-enzymatic systems. The specific and dedicated enzyme system for NO generation is not yet identified in the plants. NO helps to counteract the effects of HMs by activating various biochemical machineries such as induction of antioxidant defence systems, protein nitrosylation, programmed cell death. It is the molecule that has very promising roles and need to be explored much in relation to heavy metals.

Alterations in ultra-structures and elemental composition of ovaries of Labeo rohita (Hamilton-Buchanan) as a pollution indicator in Harike Wetland (Ramsar Site), India

ABSTRACT Teleosts are the largest class of bony fishes and account for more than 90% of fish species. Their reproductive systems are the key feature to adopt gradual evolutionary change under aquatic environmental conditions. Aquatic ecosystems are faced with a serious threat to their proliferation due to the discharge of untreated industrial effluents into them. Here, scanning electron microscopy (SEM) was used to examine the damaged ovaries of the freshwater fish Rohu, Labeo rohita (Hamilton-Buchanan), due to their exposure to different heavy metals in the polluted waters of Harike Wetland in Punjab, India. Deformed oocytes with rough and distorted surfaces were observed in SEM. Microscopic analysis showed that environmental pollution caused by municipal effluents had damaged the microstructural surface on the fish ovaries. Energy-dispersive X-ray spectroscopy also showed damage of the microstructural surface and an abnormal deposition of heavy metals. The alterations in the reproductive system of the fish appeared to be the most responsive and a reliable indicator of environmental pollution, which indicates their significance in aquatic biomonitoring systems. This is the first report in North India showing tissue level markers in biomonitoring programs using the ovary of Labeo rohita as the model system. Microscopic analysis showed that environmental pollution caused by municipal effluents damaged the microstructural surface of the fish ovaries.

Foliar dust and heavy metal deposit on leaves of urban trees in Budapest (Hungary)

This work considers dust deposition and the heavy metal (HM) content on leaves of urban trees (Acer platanoides L. ‘Globosum,’ Fraxinus excelsior L. ‘Westhof’s Glorie’ and Tilia tomentosa Moench.) in order to estimate the trees’ capacity to remove dust and HM from the air. Leaves were collected from the Buda Arboretum and from different streets of heavy traffic in Budapest, Hungary, during 2015 and 2016. At each site, five trees were sampled by collecting 6 leaves from each tree from the height of 2–3 m. Dust deposits on the leaves were removed by soaking the fresh foliage in distilled water for 20 h and then washed with ultrasound shaking. Afterward, the leaves were dried to constant weight and then they were digested in nitric acid–hydrogen peroxide treatment, and their Pb, Fe, Ni, Zn and Cu contents were measured using an inductively coupled plasma (ICP AS) spectrometer. The removed dust deposit was dried, and after a similar digestion treatment the Pb, Fe, Ni, Zn and Cu contents were measured using an AURORA AI 1200 AAS appliance. The HM deposit was calculated in mg m–2 leaf surface area. In 2015, the amount of foliar dust deposit from spring to autumn increased from 86.3 to 270.2 mg m–2. The most efficient tree species in trapping dust on their leaves was the silver linden (98.5–123.5 mg m−2), followed by the Norway maple (74.2–84.8 mg m−2) and the common ash (62.8–74.6 mg m−2). The deposit of HM elements showed seasonal differences: the quantity of Fe and Pb deposit on autumnal leaves increased five- to tenfold, while other heavy metals did not show accumulation. Silver linden with its pubescent (hairy) leaf surface proved to be most efficient in entrapping and retaining dust and heavy metals. The 60–100% higher Pb and Fe content of autumnal leaves indicate that over the season leaves may absorb Fe and Pb from the foliar dust. Our results confirmed that the foliar dust is a potential indicator for monitoring the HM content in the air. We also show that foliar dust deposits should be considered when estimating the capacity of urban trees to clean the air.

Effect of Biowastes on Soil Remediation, Plant Productivity and Soil Organic Carbon Sequestration: A Review

High anthropogenic activities are constantly causing increased soil degradation and thus soil health and safety are becoming an important issue. The soil quality is deteriorating at an alarming rate in the neighborhood of smelters as a result of heavy metal deposition. Organic biowastes, also produced through anthropogenic activities, provide some solutions for remediation and management of degraded soils through their use as a substrate. Biowastes, due to their high content of organic compounds, have the potential to improve soil quality, plant productivity, and microbial activity contributing to higher humus production. Biowaste use also leads to the immobilization and stabilization of heavy metals, carbon sequestration, and release of macro and micronutrients. Increased carbon sequestration through biowaste use helps us in mitigating climate change and global warming. Soil amendment by biowaste increases soil activity and plant productivity caused by stimulation in shoot and root length, biomass production, grain yield, chlorophyll content, and decrease in oxidative stress. However, biowaste application to soils is a debatable issue due to their possible negative effect of high heavy metal concentration and risks of their accumulation in soils. Therefore, regulations for the use of biowastes as fertilizer or soil amendment must be improved and strictly employed to avoid environmental risks and the entry of potentially toxic elements into the food chain. In this review, we summarize the current knowledge on the effects of biowastes on soil remediation, plant productivity, and soil organic carbon sequestration.

Study of Heavy Metals Variability and their Effect on Plant Growth in Kanzenze River of Upper Akagera Catchment, Rwanda

Agricultural swamps are among the major fruitful and exposed to heavy metals deposition and contributes to ecological concerns. Heavy metals are mainly pollutants to deteriorate water quality and affect plant health through leaching and seepage process from industrial services, anthropogenic activities, erosion and mining activities. The study aimed to assess heavy metals, water quality and their effect on plant growth along Kanzenze Swamp of the Akagera Upper Catchment. The total of Sixteen chemical parameters of water including Calcium, Magnesium, Sodium, Potassium, Copper, Zinc, Manganese, Lead, Cadmium, Chromium, pH, Electrical Conductivity, Sodium Adsorption Ratio, Magnesium hazards, Kelly Index and Soluble Sodium Percent were analyzed and observed values were thereafter compared with international standards values recommended by Food and Agriculture Organization. Photometric methods and Atomic Adsorption Spectrometer machines were used to detect the heavy metals while analytical. Descriptive analysis and Principal Components Analysis techniques were used to correlate water quality parameters for similarities and dissimilarities through cluster analysis. All statistical analysis were performed by using Statistical Package for Social Science version 22.0. The study findings shows that most water use for irrigation is polluted by heavy metals with maximum values compared to Rwanda national and international permissible standards for irrigation. The heavy metals with highest content included Calcium, Magnesium, Potassium, Copper, Manganese, Cadmium and Chromium. Hence farmers relaying on this water may be disposed to health hazards issues and other environmental concerns. Therefore some effective measures like water treatments are compulsory vital needed to boost the quality of water for irrigation purpose.